Add SSL certificate mode: Let's Encrypt or Wildcard per NPM

Settings > NPM Integration now allows choosing between per-customer
Let's Encrypt certificates (default) or a shared wildcard certificate
already uploaded in NPM. Includes backend, frontend UI, and i18n support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

static/lang/de.json

@@ -147,6 +147,17 @@
     "noCredentials": "Keine NPM-Zugangsdaten konfiguriert",
     "saveNpmSettings": "NPM Einstellungen speichern",
     "testConnection": "Verbindung testen",
+    "sslModeTitle": "SSL-Zertifikat Modus",
+    "sslMode": "SSL Modus",
+    "sslModeLetsencrypt": "Let's Encrypt (pro Kunde)",
+    "sslModeWildcard": "Wildcard-Zertifikat",
+    "sslModeHint": "Waehlen Sie, ob jeder Kunde ein eigenes Let's Encrypt Zertifikat erhaelt oder ein gemeinsames Wildcard-Zertifikat verwendet wird.",
+    "wildcardCertificate": "Wildcard-Zertifikat",
+    "selectCertificate": "-- Zertifikat waehlen --",
+    "wildcardCertHint": "Waehlen Sie das Wildcard-Zertifikat (z.B. *.example.com), das bereits in NPM hochgeladen ist.",
+    "noWildcardCerts": "Keine Wildcard-Zertifikate in NPM gefunden.",
+    "certsLoaded": "{count} Wildcard-Zertifikat(e) gefunden.",
+    "expiresOn": "Ablaufdatum",
     "managementImage": "Management Image",
     "managementImagePlaceholder": "netbirdio/management:latest",
     "signalImage": "Signal Image",

static/lang/en.json

@@ -147,6 +147,17 @@
     "noCredentials": "No NPM credentials configured",
     "saveNpmSettings": "Save NPM Settings",
     "testConnection": "Test Connection",
+    "sslModeTitle": "SSL Certificate Mode",
+    "sslMode": "SSL Mode",
+    "sslModeLetsencrypt": "Let's Encrypt (per customer)",
+    "sslModeWildcard": "Wildcard Certificate",
+    "sslModeHint": "Choose whether each customer gets an individual Let's Encrypt certificate or uses a shared wildcard certificate.",
+    "wildcardCertificate": "Wildcard Certificate",
+    "selectCertificate": "-- Select certificate --",
+    "wildcardCertHint": "Select the wildcard certificate (e.g. *.example.com) already uploaded in NPM.",
+    "noWildcardCerts": "No wildcard certificates found in NPM.",
+    "certsLoaded": "{count} wildcard certificate(s) found.",
+    "expiresOn": "Expires",
     "managementImage": "Management Image",
     "managementImagePlaceholder": "netbirdio/management:latest",
     "signalImage": "Signal Image",